1. Field of the Invention
The present invention relates to management of a power-saving mode, and in particular, to an apparatus and method for managing a power-saving mode (e.g., an idle mode and a sleep mode) of a portable terminal.
2. Description of the Related Art
In a 4th Generation (4G) communication system, research is actively being conducted to provide users with a variety of Quality of Services (QoSs) at a high data transfer rate of about 100 Mbps. In particular, in a Broadband Wireless Access (BWA) communication system such as a Local Area Network (LAN) system or a Metropolitan Area Network (MAN) system, research is being conducted so that high-speed service can be supported while ensuring mobility and QoS. One example of such a communication system includes the BWA communication system based on the Institute of Electrical and Electronics Engineers (IEEE) 802.16d standard or the IEEE 802.16e standard.
The system based on the IEEE 802.16d standard or the IEEE 802.16e standard employs an Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) scheme so that a physical channel of the wireless MAN system can support a broadband access network. The communication system based on the IEEE 802.16d is implemented in consideration of only a single cell structure in a state that a Subscriber Station (SS) is fixedly located, that is, a mobility of the SS is not taken into consideration. The communication system based on the IEEE 802.16e is improved from the communication system based on the IEEE 802.16d in a sense that a mobility of the SS is taken into consideration. An SS providing mobility is defined as a Mobile Station (MS). Hereinafter, the SS and the MS will be referred to as a portable terminal, and the portable terminal includes all terminals that can be carried by a user.
The communication system based on the IEEE 802.16e standard can offer optimal data transfer efficiency with a high speed data transfer rate since orthogonality is maintained among a plurality of sub-carriers while transferring data. Further, good frequency usage efficiency and strong multi-path fading also facilitate the optimal data transfer efficiency.
The OFDM/OFDMA scheme uses a technique whereby a sub-channel is formed to use a sub-carrier which is shared to enhance channel efficiency between a Base Station (BS) and a plurality of portable terminals located within one cell, and the sub-carrier is then assigned to a portable terminal.
Examples of the communication system based on the IEEE802.16 die include Wimax, Wibro, and Mobile Wimax systems. A portable terminal employing a Wibro technique is generally implemented in the form of a notebook computer in which a Personal Computer Memory Card International Association (PCMCIA) card is included in a built-in manner or in the form of a personal portable terminal such as Personal Digital Assistant (PDA).
A portable terminal compliant with the IEEE 802.16e standard supports high-speed data communication, resulting in large amount of power consumption. Therefore, a power-saving mode has been introduced in the IEEE 802.16e standard so as to reduce power consumed in the portable terminal.
The power-saving mode is roughly classified into two modes, an idle mode and a sleep mode. First, the idle mode is provided to save power as well as unused wireless resources of the portable terminal. While in the idle mode, a message which is broadcast from a BS is periodically received in a state that connection between the portable terminal and the BS is released. Transition to the idle mode may be achieved when the portable terminal sends a request to the BS. Also, transition to the idle mode may be achieved in response to an instruction of the BS without the request of the portable terminal.
Second, the sleep mode is defined as a mode in which wireless resources are not used for a predetermined period of time while the portable terminal is operating. A time period for using a wireless resource is defined as a listen window, and a time period for not using the wireless resource is defined as a sleep window.
FIG. 1 illustrates an operation of a conventional power-saving mode.
In FIG. 1, the IEEE 802.16e standard describes how a transition is made from an idle mode or sleep mode to a normal mode in a modem 120 of a portable terminal. However, the existing IEEE 802.16e standard does not describe how a power-saving mode of a host (i.e., Central Processing Unit (CPU) in a host) 100 is related to that of the modem 120. Furthermore, mode transition and mode management performed between the host 100 and the modem 120 are not described.
The conventional power-saving mode has a problem. For example, the modem 120 may not switch to a sleep mode or an idle mode while the host 100 has switched to a power-saving mode. In this case, power may be continuously consumed by the modem 120, resulting in waste of power.
Accordingly, there is a needed an apparatus and method for reducing power consumption by allowing a modem to switch to a suitable power-saving mode according to a state of a power-saving mode in a host side and according to a network traffic type used in an application program.